#!/usr/bin/perl

use strict;
use warnings;

use Data::Dumper;

my @binarray;

while (<DATA>)
{
    my ($x,$y)=split / +/;
    
    my $ax = [ (0) x 72 ];
    my $ay = [ (0) x 72 ];
    
    $ax->[int ($x+180) / 5] = 1;
    $ay->[int ($y+180) / 5] = 1;
    
    push @binarray, [$ax, $ay];
}

print Dumper (\@binarray);


__DATA__
-70.6     -27.5 
-60.8      52.9
-123.0    -132.9 
110.1     119.9 
-62.4     -45.6
[download]

I think your code is fine, though it could be made more succinct without sacrificing clarity, and it has a strong "C accent". :-). Here's how I would "perlify" it:

use strict;
use warnings;
my $input    = shift;
my $min      = -180;
my $range    = 360;
my $bin_size = 5;
my $n_bins   = $range/$bin_size;
my @binarray = map [ ( 0 ) x $n_bins ], 1..$n_bins;
  
open my $in, $input or die "Oops! Can't open $input: $!\n";
while ( <$in> ) {
  my @indices = map to_index( $_ ), split;
  $binarray[$indices[ 0 ]][$indices[ 1 ]]++;
}
close $in or die "Failed to close $input: $!\n";

for my $row ( @binarray ) {
  print "$_\n" for @$row;
}

sub to_index {
  return ( $_[ 0 ] - $min )/$bin_size;
}
[download]

Thanks. Yeah, well my strongest programming language is C, and I have been using it for a lot longer than I have been using perl (although i would not claim to be an expert at C even and am certainly a novice at perl!) so I guess its not surprising my code is a bit 'C' like in nature :)

Thanks for the tips. I'll make a perl programmer yet (in about a decade or so maybe ... lol.)

... but is the approach I used a reasonably sensible one in your opinion?

You have only described the manipulations you are doing to create your graph. Without some idea about what the raw data represents and what you are hoping to discover (or just show) with your graph, it is impossible to say whether your manipulations are good or not.